Isolated LED Power Supply Shutdown for Micro Short Protection
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Solution Overview
Problem
Conventional LED power supplies fail to activate short-circuit protection when micro short circuits occur, leading to potential fires, especially under constant-voltage/constant-current control, due to insufficient overload protection margins and inability to reduce output current during abnormal conditions.
Innovation Solution
An LED power supply employing constant-voltage/constant-current control with a control module that includes an isolated DC-DC conversion circuit, feedback circuit, and optocoupler, which triggers protection when the output voltage drops below a threshold, instantly stopping operation to prevent damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If constant-voltage/constant-current control is adopted to reduce overload protection margin, then the power supply can operate efficiently under normal conditions, but the power supply fails to activate protection when micro short circuits occur due to insufficient voltage drop detection
Solution Approach 1:
The control circuit is segmented into two independent protection mechanisms: overcurrent protection through constant-current control and low-voltage protection through the voltage detection circuit. This segmentation allows each mechanism to handle specific failure modes independently, resolving the contradiction by adding targeted protection without requiring complete circuit redesign.
Solution Approach 2:
A voltage detection circuit acts as an intermediary between the output terminals and the control unit. This intermediary component specifically detects voltage drops caused by micro short circuits and triggers protective action, addressing the detection gap in conventional constant-voltage/constant-current control systems without complicating the overall control architecture.
2Reliability
If the triggering current of overcurrent protection is set higher than full-load current by 30% margin, then false triggering is avoided, but the design cannot meet UL Class 2 requirements for 24V/100W output
Solution Approach 1:
The protection system dynamically switches between constant-voltage mode and constant-current mode based on load conditions. During normal operation, constant-voltage mode provides full power output; when overload or short circuit occurs, the system dynamically transitions to constant-current mode or activates low-voltage protection, resolving the contradiction between protection sensitivity and power output capacity.
Solution Approach 2:
The system changes operating parameters dynamically: under normal conditions it maintains constant voltage for maximum power delivery, but detects voltage drops and transitions to constant-current control or protection mode when abnormalities occur. This parameter change strategy allows meeting both UL Class 2 power requirements and protection accuracy without fixed 30% margin limitation.
3Ease of operation
If constant-voltage control is used with fixed output voltage, then the power supply operates simply under normal load, but the output current increases excessively under overload conditions causing false triggering
Solution Approach 1:
The power supply dynamically adjusts its control mode based on operating conditions: it operates in simple constant-voltage mode during normal conditions for ease of operation, but automatically transitions to constant-current mode or activates low-voltage protection when overload or short circuit occurs, thereby maintaining both operational simplicity and protection reliability.
Solution Approach 2:
The voltage detection circuit provides continuous feedback about output voltage conditions to the control unit. This feedback mechanism allows the system to maintain simple constant-voltage operation during normal conditions while automatically detecting abnormal voltage drops and triggering protective actions, resolving the contradiction between operational simplicity and protection reliability.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively protects the LED power supply and connected devices by instantly halting operation upon detecting abnormal output voltage, preventing fires and damage from micro short circuits.
Implementation Method 1
The optocoupler is configured for signal transmission with electrical isolation and includes a transmitter and a receiver electrically connected to the secondary side and the first control unit respectively
Data Source
AI summary
An LED power supply is provided. The LED power supply adopts constant-voltage/constant-current control, supplies power to an LED device, and includes an isolated DC-DC conversion circuit having primary and secondary sides and a control module. The control module includes a control unit, a feedback circuit, first and second switches and an optocoupler. The control unit is electrically connected to the primary side and controls operation of the conversion circuit. The optocoupler is configured for signal transmission with electrical isolation and includes a transmitter and a receiver electrically connected to the secondary side and the control unit respectively. When the output voltage is lower than a threshold voltage, the first switch is turned off, the second switch is turned on to trigger the optocoupler to generate a trigger signal at the receiver, and the control unit controls the isolated DC-DC conversion circuit to stop operating based on the trigger signal.